Extended Graph Unification

We propose an apparently minor extension to Kay's (1985} notation for describing directed acyclic graphs (DAGs}. The proposed notation permits concise descriptions of phenomena which would otherwise be difficult to describe, without incurring significantextra computational overheads in the process of unification. We illustrate the notation with examples from a categorial description of a fragment of English, and discuss the computational properties of unification of DAGs specified in this way. argue that our extension makes it possible to describe any phenomena which could not have been described at all using the existing notations, just that the descriptions using the extension are more concise. 2 GRAPH SPECIFICATION We start by defining a language GSL (graph specification language} for describing graphs, and by specifying the conditions under which two graphs unify.

• Type: Conference
• Year: 1989
• Where: EACL
• Authors: Allan Ramsay
• Keywords: Acyclic Graphs, EACL 1989, Natural Language Processing, Permits Concise Descriptions, Significantextra Computational Overheads